1. Field of the Invention
The present invention relates to an optical connector plug which is used for connecting optical cables for an optical communication system.
2. Description of the Related Art
An optical connector plug a, as a conventional art, as shown in FIGS. 9 to 12 comprises: an optical fiber cable b; an optical fiber c which is exposed by exfoliating a coating of a front end of the optical fiber cable b; a microhole d which pierces an axis of the optical fiber c; a holder e; a ferrule f in which the optical fiber c penetrates the microhole d and is fixed and which is armored and fixed at a rear end thereof by the holder e; a coil spring g which is armored by a rear portion of the holder e and is interposed between a stop ring i and an enlarging portion e1 at a front end of the holder e; a pair of arcuate projected bands h; the stop ring i, which is armored by the rear portion of the holder e from a substantially intermediate portion and on which the pair of arcuate projected bands h is symmetrically provided for a circumferential wall of the optical fiber c in the circumferential direction; four groove portions j which are provided at the enlarging portion e1 of the holder e; two latching projected bands k which are latched together to the four groove portions j to be opposed to each other, at a substantially intermediate portion of an inside wall of the optical fiber c; a pair of engaging holes 1 with which the pair of the arcuate projected bands h of the stop ring i is engaged; and a plug frame m which the pair of engaging holes 1 pierces to be opposed to each other.
In the optical connector plug a as the conventional art, the stop ring i and the plug frame m are combined and fixed and the stop ring i is unrotatable. To reduce an eccentric error, the ferrules f are positioned, that is, the eccentricity between optical axes of the ferrules f is corrected in advance upon assembly. However, in general, a core of the optical fiber is eccentric in some degree in terms of the accuracy upon manufacturing. As shown in FIGS. 13 and 14, when a core o of an optical fiber c in one optical connector plug a is connected to a core p of an optical fiber c1 in another optical connector plug a1 to face each other, the optical axes of the cores o and p are made eccentric and, thus, the loss of the connection is also caused.
Incidentally, referring to FIGS. 13 and 14, reference symbol f denotes a ferrule of the one optical connector plug a and f1 denotes a ferrule of the other optical connector plug a1.
Further, conventionally, an optical connector plug, as a mechanism for correcting the eccentricity of optical axes of ferrules after assembly, is put into practical use. In the optical connector plug, a positioning key is arranged to fix the ferrules to a determined position at which the loss of the connection is the most small by rotating the ferrules. However, since adjustment in a single step is impossible, the precise correction cannot be performed against the eccentricity of the optical axes.
To solve the above-mentioned problems in the conventional optical connector plugs, it is an object of the present invention to provide an optical connector plug, in which the eccentricity of optical axes of ferrules integral with a stop ring can be adjusted in a single step and can precisely be corrected by rotating the stop ring relative to a plug frame after assembling the optical connector plug, and the ferrules can easily and certainly be fixed to a correcting position without using a positioning key.
To accomplish the above-mentioned object, according to a first aspect of the present invention, there is provided an optical connector plug comprising: a holder having a ferrule at one end thereof; a stop ring for supporting the ferrule in a predetermined direction; a plug frame for rotatably supporting and incorporating the stop ring in an axial direction; and a coil spring interposed between the holder and the stop ring, for energizing the ferrule to the front in the plug frame, wherein the holder and the stop ring have engaging portions with which they are mutually engaged, and an eccentric error of an optical axis of the ferrule is adjusted in a single step by rotating the stop ring and fixing the plug frame or by rotating the plug frame and fixing the stop ring, and an adjusted position is fixed by pressure generated by pressing the spring to the holder.
According to a second aspect of the present invention, there is provided an optical connector plug comprising: a holder having a ferrule at one end thereof; a stop ring for supporting the ferrule in a predetermined direction; a plug frame for rotatably supporting and incorporating the stop ring in an axial direction; and a coil spring interposed between the holder and the stop ring, for energizing the ferrule to the front in the plug frame, wherein the holder and the stop ring have engaging portions with which they are mutually engaged, and an optical axis of the ferrule is adjusted in a single step by rotating the stop ring and fixing the plug frame or by rotating the plug frame and fixing the stop ring, and an adjusted position is fixed by pressure generated by pressing the spring to the holder and by using an adhering agent which is filled between the plug frame and the stop ring.
According to a third aspect of the present invention, there is provided an optical connector plug comprising: a holder having a ferrule at one end thereof; a stop ring for supporting the ferrule in a predetermined direction; a plug frame for rotatably supporting and incorporating the stop ring in an axial direction; and a coil spring interposed between the holder and the stop ring, for energizing the ferrule to the front in the plug frame, wherein the holder and the stop ring have engaging portions with which they are mutually engaged, and the entire of the stop ring is formed as a single substantially-cylindrical structure, and the stop ring is rotated round the axis in the plug frame and is fit while it is prevented from the movement in the axial direction.
Preferably, in the optical connector plug, the engaging portion of the holder may be a latching groove, and the engaging portion of the stop ring may be an engaging projection.
Preferably, in the optical connector plug, the engaging portion of the holder may be a latching projection, and the engaging portion of the stop ring may be a latching groove.
Preferably, in the optical connector plug, a pair of latching holes, which penetrates a circumferential wall of the plug frame to be opposed to each other, may be provided for the circumferential wall and a ring-shaped projected band for being fit into the latching hole may be provided for a circumferential portion of the stop ring.
The ferrule is rotatably inserted in the center of the inside of the plug frame around the axis thereof and, thereafter, the coil spring is interposed between the ferrule and the holder and the front portion of the stop ring is pressed and is fit into the plug frame. Then, the target portions at the peripheral edges in the ring-shaped projected bands, which are arranged to the periphery of the stop ring, are fit into the pair of latching holes that are formed by penetrating a circumferential wall of the plug frame to be opposed to each other. In this case, the engaging portions at the end of the stop ring are latched together to the engaging portions of the holder and, then, the assembling operation is completed.
One optical connector plug having the above structure is fit into an optical adapter from one opening of the optical connector. A ferrule of the one optical plug faces a ferrule of another optical connector plug which is fit into the optical adapter from another opening. Thus, cores of both the ferrules are connected to face each other.
The eccentric error upon connecting both the ferrules is detected by a well-known detector. If there is an eccentric error, the stop ring is rotated around the axis thereof while the optical connector plug is fit and hold into the optical adapter. Then, the stop ring is rotated around the axis thereof in a single step, relative to the plug frame and, consequently, the ferrules are rotated round the axis via the holder having the engaging portions which are engaged with the engaging portion of the stop ring.
The stop ring is rotated while the detector detects the eccentric error which is caused by connecting the cores of the ferrules. Then, the stop ring stops rotating at the position at which the eccentric error is absent or at the position at which the eccentric error is the smallest, thereby adjusting the eccentric error. By stopping rotating the stop ring at the adjusted position, the stop ring is fixed by pressure generated by pressing the coil spring to the holder. Further, the adhering agent is filled between the plug frame and the stop ring, thereby fully being fixed.
In the present invention, as mentioned above, the eccentric error can be adjusted in a single step and the adjusted position can be fixed by rotating the ferrule, that is, the optical fiber in the circumferential direction, relative to the plug frame. Therefore, the eccentric error can be reduced as much as possible and the connecting loss upon facing the both cores of the ferrules can greatly be reduced.
After assembling the optical connector plug, the ferrule, in other words, the optical fiber can be rotated at the same position without the forward and backward movement by rotating the stop ring together with the coil spring and boot in the circumferential direction, relative to the plug frame. Thus, the eccentric error of the both cores can easily and accurately be adjusted, and the connecting loss upon facing the both cores can greatly be reduced.